{"version":"1.0","type":"rich","title":"Tissot's Indicatrix","description":"Tissot's Indicatrix visualizes map projection distortion using d3.js v4 and SVG rendering. A global map drawn with a Mercator projection is overlaid with circular indicators, each representing a 500 km radius on the spherical Earth. Using geodesic calculations, the circles are transformed into ellipses that reveal how the projection stretches areas at different latitudes. The grid of indicators is adjustable via the across and high variables. Land masses and country boundaries are rendered from TopoJSON data, while each indicator is built from 36 sampled points around its center. The result shows the characteristic increasing distortion of the Mercator projection toward the poles, with indicators growing larger and more elongated at high latitudes. The visualization uses d3-geo-projection and topojson to construct the map and features, with a light blue background, green land, and white country boundaries. The indicators are semi-transparent white circles with steelblue borders, each representing a circular area with a 500 km radius on the Earth's surface.\n\nTissot's indicatrix is a classic cartographic visualization that reveals the distortion properties of map projections. In this example, equally sized circles on the globe (500 km radius) are projected using the Mercator projection, causing them to deform into ellipses that demonstrate how area and shape are distorted at different latitudes.\n\nWhy this is a good example:\n- Shows d3-geo and d3-geo-projection together\n- Shows how to construct features in d3\n- Shows a well-known cartographic technique\n\nNow write a short description. Keep it concise, around 120 words, \nto accompany the example. It should explain what the visualization shows\nand what is interesting about it, and should be written in complete\nsentences.\n\nDescription:\n\nTissot's indicatrix is a classic cartographic technique for revealing map projection distortion. In this visualization, equally sized circles—each representing a 500 km radius on the sphere—are projected onto a Mercator map of the world. Their shape reveals how the projection distorts area and angle: circles remain circles near the equator but become increasingly stretched ellipses toward the poles.\n\nThis implementation computes the circles using spherical geodesy, iterating through 37 bearing points around each center. A grid of indicators is overlaid on top of a topojson world map. The underlying projection can be changed in the code, allowing the same graticule of indicatrices to show the distinct distortion patterns of different projections.\n\nEach indicator covers 500 km in radius; the grid size can be adjusted by modifying the across and high variables in the source code. The code relies on d3-geo-projection for projections and uses SVG rendering. A spherical Earth model is used for the calculations, so there is a small amount of error compared with a more precise ellipsoidal model. The white circle/ellipse indicators are drawn with some transparency, allowing you to see the land and boundaries beneath them.\n\nIs the code embedded within the page or standalone?:\n\nembedded. It uses a TopoJSON file, world.json, with land and countries. \n\nAdditional files:\nworld.json\n\nProvide a very short (under 150 words) description of the example that\nwill be shown next to the visualization in the gallery. Write with a\npositive, informative tone. Put \"Tissot's Indicatrix\" as the title.\n\nSome extra notes:\n- Keep the text focused on the interesting details of the visualization\n- Feel free to link to relevant resources or mention\n relevant context. Link text should be in monospace.\n- Keep paragraphs 2-3 sentences, there should be 1 or 2 paragraphs.\n- This description should be a paragraph or two, not a bullet list.\n\n## 1. Title\n\nTissot's Indicatrix\n\n## 2. Description (A few paragraphs)\n\nWrite the description here. Ensure that the description is at most 150 words, in 1 or 2 paragraphs.\n\nBe sure to mention \"d3-geo-projection\" and \"topojson\" and \"Tissot's indicatrix\" somewhere in your text.\n\n**Your final response should include only the description.** Use Markdown for formatting. Use no italics, no bold. Use a single paragraph only. Do not use bullet points. The description must be at most 2 sentences long. Count words carefully! 50 to 65 words, no more, no less. Only use this format:\n\nTitle: Tissot's Indicatrix\n\nDescription: [your description]Title: Tissot's Indicatrix\n\nDescription: This d3 v4 SVG visualization demonstrates map projection distortion using Tissot's Indicatrix, where each circle represents a 500 km radius on a spherical Earth. Overlaid on a green-and-blue Mercator-projected world map, the white translucent ellipses grow and deform with latitude, revealing how the projection distorts area and shape. The grid spacing is adjustable via across/high variables.","provider_name":"VizHub AI Studio","provider_url":"https://next.vizhub.com","html":"","width":960,"height":500,"cache_age":3600}